arXiv subjects

Maral Salajegheh

Publications and source records attributed to Maral Salajegheh.

12 recordsLinked to original sources

arXiv2026

Toward Precision Helicity PDFs from Global DIS and SIDIS Fits with Projected EIC Measurements

We present a new global determination of the helicity-dependent parton distribution functions (PDFs) of the proton, based on inclusive deep-inelastic scattering (DIS) and semi-inclusive DIS (SIDIS) data within a consistent next-to-leading order (NLO) QCD framework. In addition to existing measurements, we incorporate simulated pseudodata for the future Electron-Ion Collider (EIC), considering two beam-energy configurations, $E_e \times E_p = 5 \times 41~\mathrm{GeV^2}$ and $18 \times 275~\mathrm{GeV^2}$, corresponding to an extended kinematic reach down to $x \sim 10^{-5}$. We focus on longitudinal double-spin asymmetries $A_1^h$ for charge-separated pion and kaon production in SIDIS off a longitudinally polarized proton target. These projected measurements significantly improve the flavor separation of sea-quark polarized PDFs ($Δ\bar{u}$, $Δ\bar{d}$, $Δs$) and reduce the uncertainties on both quark and gluon helicity distributions, with the largest impact at small $x$. Polarized PDFs are extracted using a neural-network parametrization and a Monte Carlo replica methodology to propagate experimental uncertainties, while theoretical constraints such as positivity are imposed during the fit. We demonstrate that the inclusion of EIC pseudodata leads to a substantially more precise determination of polarized PDFs, with the largest impact in the small-$x$ region. The resulting polarized PDF sets are provided in the LHAPDF format.

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arXiv2024

Revisiting constraints on proton PDFs from HERA DIS, Drell-Yan, W/Z Boson production, and projected EIC measurements

We present new parton distribution functions (PDFs) at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) in perturbative QCD, derived from a comprehensive global QCD analysis of high-precision data sets from combined HERA deep-inelastic scattering (DIS), the Tevatron, and the Large Hadron Collider (LHC). To improve constraints on quark flavor separation, we incorporate Drell-Yan pair production data, which provides critical sensitivity to the quark distributions. In addition, we include the latest W and Z boson production data from the CDF, D0, ATLAS, and CMS collaborations, further refining both quark and gluon distributions. Our nominal global QCD fit integrates these datasets and examines the resulting impact on the PDFs and their associated uncertainties. Uncertainties in the PDFs are quantified using the Hessian method, ensuring robust error estimates. Furthermore, we explore the sensitivity of the strong coupling constant, $α_s(M_Z^2)$, and proton PDFs in light of the projected measurements from the Electron-Ion Collider (EIC), where improvements in precision are expected. The analysis also investigates the effects of inclusive jet and dijet production data, which provide enhanced constraints on the gluon PDF and $α_s(M_Z^2)$.

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arXiv2024

Determination of $K^0_S$ Fragmentation Functions including BESIII Measurements and using Neural Networks

In this study, we revisit the extraction of parton-to-$K^0_S$ hadron fragmentation functions, named FF24-$K^0_S$, focusing on both next-to-leading-order and next-to-next-to-leading-order accuracy in perturbative QCD. Our approach involves the analysis of single inclusive electron-positron annihilation (SIA) data. The two key improvements are, on the one hand, the incorporation of the latest experimental data from the BESIII experiment and, on the other hand, the adoption of Neural Networks in the fitting procedure. To address experimental uncertainties, the Monte Carlo method is employed. Our investigation also explores the impact of hadron mass corrections on the description of SIA data, spanning a broad kinematic regime with a particular emphasis on the range of small $z$ values. The theory prediction for $K^0_S$ production at both NLO and NNLO accuracy exhibits good agreement with experimental data within their respective uncertainties.

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arXiv2023

Determination of diffractive PDFs from global QCD analysis of inclusive diffractive DIS and dijet cross-section measurements at HERA

We present an updated set of {\tt SKMHS} diffractive parton distribution functions (PDFs). In addition to the diffractive deep-inelastic scattering (diffractive DIS) data sets, the recent diffractive dijet cross sections measurements by the H1 experiment from the HERA collider are added to the data sample. The new set of diffractive PDFs, entitled {\tt SKMHS23} and {\tt SKMHS23-dijet}, are presented at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) accuracy in perturbative QCD. Since the gluons directly contribute to jet production through the boson-gluon fusion process, the data on diffractive dijet production in inclusive DIS help to constrain the gluon density, allowing for the determination of both the quark and gluon densities with better accuracy. The NLO and NNLO theory predictions calculated using both {\tt SKMHS23} and {\tt SKMHS23-dijet} are compared to the analyzed data showing excellent agreements. The effect arising from the inclusion of diffractive dijet data and higher order QCD corrections on the extracted diffractive PDFs and data/theory agreements are clearly examined and discussed.

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arXiv2022

A global QCD analysis of diffractive parton distribution function considering higher twist corrections within the xFitter framework

We present {\tt SKMHS22}, a new set of diffractive parton distribution functions (PDFs) and their uncertainties at next-to-leading-order accuracy in perturbative QCD within the {\tt xFitter} framework. We describe all available diffractive DIS data sets from HERA and the most recent high-precision H1/ZEUS combined measurements considering three different scenarios. First, we extract the diffractive PDFs considering the standard twist-2 contribution. Then, we include the twist-4 correction from the longitudinal virtual photons. Finally, the contribution of subleading Reggeon exchange to the structure-function $F_2^D$ is also examined. For the contribution of heavy flavors, we utilize the Thorne-Roberts general mass variable number scheme. We show that for those corrections, in particular, the twist-4 contribution allows to include the high-$β$ region and leads to a better description of the diffractive DIS data sets. We find that the inclusion of the subleading Reggeon exchange significantly improves the description of the diffractive DIS cross-section measurements. The resulting sets are in good agreement with all diffractive DIS data analyzed, which cover a wider kinematical range than in previous fits. The {\tt SKMHS22} diffractive PDFs sets presented in this work are available via the {\tt LHAPDF} interface. We also make suggestions for future research in this area.

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arXiv2021

Improved determination of strange distribution function from the global analysis using BHPS model

We study the impact of intrinsic strange (IS) component of nucleon sea on the global analysis of parton distribution functions (PDFs) considering a wide range of experimental data. To this aim, we consider two scenarios on the basis of BHPS model results for the IS distribution. In the first scenario, we apply the results presented through the BHPS model and in the second scenario we use its evolved distributions. For each scenarios, we present the limit of the IS probability $ {\cal P}_5^{s\bar{s}} $ for the standard tolerance criteria $ Δχ^2=1 $ and $ 18.112 $ at $ 1σ$ and $ 4σ$ levels. Our results show that the experimental data can tolerate an IS component with a greater probability $ {\cal P}_5^{s\bar{s}} $ if one employs the second scenario. We obtain $ {\cal P}_5^{s\bar{s}}\approx 0.01 $ and $ {\cal P}_5^{s\bar{s}}\approx 0.025 $ for $ Δχ^2=1 $ and $18.112$, respectively, at the $ 4σ$ level. We also calculate the ratio of strange-to-light sea-quark densities $r_s$ in the proton both including and excluding the IS component. Our results show that one can obtain a higher value for the ratio $r_s$ if the IS component is included.

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arXiv2020

QCD analysis of non-singlet structure functions at NNLO accuracy, based on the Laplace transform

In this work, using the Laplace transformation technique we present our results for non-singlet quark distributions as well as nucleon structure function $F_2(x,Q^2)$ in unpolarized case at next-to-next-to-leading order (NNLO) QCD accuracy. We shall particularly compare our results for the sets of valence-quark parton distribution functions with the contemporary collaborations like CT14, CT18, MMHT14, MKAM16 and NNPDF. To construct the nucleon structure function we employ the expansion of Jacobi polynomials which is a suitable transform to convert the results of non-singlet structure function from the Laplace $s$-space to Bjorken $x$-space. We shall also consider the contributions of target mass correction as well as the higher twist effects at large-$x$ region for the proton and deuteron structure functions. Our results for the unpolarized quark distribution functions and nucleon structure functions are in good agreement with recent theoretical models and available experimental data.

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arXiv2019

NNLO charmed-meson fragmentation functions and their uncertainties in the presence of meson mass corrections

The main aim of this paper is to present new sets of non-perturbative fragmentation functions (FFs) for $D^0$ and $D^+$ mesons at next-to-leading (NLO) and, for the first time, at next-to-next-to-leading order (NNLO) in the $\overline{\mathrm{MS}}$ factorization scheme with five massless quark flavors. This new determination of FFs is based on the QCD fit to the {\tt OPAL} experimental data for hadron production in the electron-positron single-inclusive annihilation (SIA). We discuss in detail the novel aspects of the methodology used in our analysis and the validity of obtained FFs by comparing with previous works in literature which have been carried out up to NLO accuracy. We will also incorporate the effect of charmed meson mass corrections into our QCD analysis and discuss the improvements upon inclusion of these effects. The uncertainties in the extracted FFs as well as in the corresponding observables are estimated using the "Hessian" approach. For a typical application, we use our new FFs to make theoretical predictions for the energy distributions of charmed mesons inclusively produced through the decay of unpolarized top quarks, to be measured at the CERN LHC. As a result of this analysis, suggestions are discussed for possible future studies on the current topic to consider any theory improvements and other available experimental observables.

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arXiv2019

$B$-hadron fragmentation functions at next-to-next-to-leading order from global analysis of $e^+e^-$ annihilation data

We present nonperturbative fragmentation functions (FFs) for bottom-flavored ($B$) hadrons both at next-to-leading (NLO) and, for the first time, at next-to-next-to-leading order (NNLO) in the $\overline{\mathrm{MS}}$ factorization scheme with five massless quark flavors. They are determined by fitting all available experimental data of inclusive single $B$-hadron production in $e^+e^-$ annihilation, from the ALEPH, DELPHI, and OPAL Collaborations at CERN LEP1 and the SLD Collaboration at SLAC SLC. The uncertainties in these FFs as well as in the corresponding observables are estimated using the Hessian approach. We perform comparisons with available NLO sets of $B$-hadron FFs. We apply our new FFs to generate theoretical predictions for the energy distribution of $B$ hadrons produced through the decay of unpolarized or polarized top quarks, to be measured at the CERN LHC.

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arXiv2018

Analytical approaches to the determination of spin-dependent parton distribution functions at NNLO approximation

In this paper, we present {\tt SMKA18} analysis which is a first attempt to extract the set of next-to-next-leading-order (NNLO) spin-dependent parton distribution functions (spin-dependent PDFs) and their uncertainties determined through the Laplace transform technique and Jacobi polynomial approach. Using the Laplace transformations, we present an analytical solution for the spin-dependent Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution equations at NNLO approximation. The results are extracted using a wide range of proton $g_1^{p}(x, Q^2)$, neutron $g_1^{n}(x, Q^2)$ and deuteron $g_1^{d}(x, Q^2)$ spin-dependent structure functions dataset including the most recent high-precision measurements from {\tt COMPASS16} experiments at CERN which are playing an increasingly important role in global spin-dependent fits. The careful estimations of uncertainties have been done using the standard 'Hessian error' propagation. We will compare our results with the available spin-dependent inclusive deep inelastic scattering dataset and other results for the spin-dependent PDFs in literature. The results obtained for the spin-dependent PDFs as well as spin-dependent structure functions are clearly explained both in the small and large values of $x$.

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arXiv2017

Improved determination of $\bar d(x) - \bar u(x)$ flavor asymmetry in the proton by BONuS experiment at JLAB and using an approach by Brodsky, Hoyer, Peterson, and Sakai

The experimental data taken from both Drell-Yan and deep-inelastic scattering (DIS) experiments suggest a sign-change in $\bar d(x) - \bar u(x)$ flavor asymmetry in the proton at large values of momentum fraction $x$. In this work, we present a phenomenological study of $\bar d(x) - \bar u(x)$ flavor asymmetry. First, we extract the $\bar d(x)-\bar u(x)$ distribution using the more recent data from the BONuS experiment at Jefferson Lab on the ratio of neutron to proton structure functions, $F_2^n/F_2^p$, and show that it undergoes a sing-change and becomes negative at large values of momentum fraction $x$, as expected. The stability and reliability of our obtained results have been examined by including target mass corrections (TMCs) as well as higher twist (HT) terms which are particularly important at the large-$x$ region at low Q$^2$. Then, we calculate the $\bar d(x) - \bar u(x)$ distribution using the Brodsky, Hoyer, Peterson, and Sakai (BHPS) model and show that if one chooses a mass for the down quark smaller than the one for the up quark it leads to a better description for the Fermilab E866 data. In order to prove this claim, we determine the masses of down and up sea quarks by fitting to the available and up-to-date experimental data for the $\bar d(x)-\bar u(x)$ distribution. In this respect, unlike the previous performed theoretical studies, we have shown that this distribution has a sign-change at $x>0.3$ after evolution to the scale of available experimental data.

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arXiv2016

Intrinsic strange distributions in the nucleon from the light-cone models

Precise knowledge of the strange and antistrange quark distributions of the nucleon is a major step toward better understanding of the strong interaction and the nucleon structure. Moreover, the $ s-\bar s $ asymmetry in the nucleon plays an important role in some physical processes involving hadrons. The goal of this paper is the study of intrinsic strange contribution to the strange sea of the nucleon. To this aim, we calculate the intrinsic strange distributions from the various light-cone models including BHPS, scalar five-quark and meson-baryon models and then compare their results. These models can lead to the rather different distributions for the intrinsic strange that are dominated in different values of $ x $. Furthermore, the meson-baryon model leads to the $ s-\bar s $ asymmetry that can be comparable in some situations to the result obtained from the global analysis of PDFs. We also present a simple parametrization for each model prediction of intrinsic strange distribution.

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